1. Field of the Invention
The invention relates to a method and an apparatus for producing rolls from endless, flexible, sheet-form material and, more particularly, to a method and an apparatus for producing rolls at high speeds with different operating systems.
Apparatuses for producing rolls are known. They serve for the initial winding-up or re-winding of woven or non-woven fabrics, papers, films or composite materials, which may be plastically and/or elastically deformable, which may have an adhesive coating or shrinking properties, and which may have dimensions and material properties that are very different in every respect.
A frequent use of such winders is for winding up plastics films which are produced in an upstream blow-molding or slot extruder.
The diameters and lengths of the winding cores and the outside diameters of the rolls may be very different. The thicknesses of the materials to be wound up lie in the range of 5-1000 .mu.m, and the speeds of the material fed in vary between 1 and 1000 m/min.
The requirements for these winders are very varied, corresponding to the properties, dimensions and feed rates of the materials to be wound up as well as to the dimensions and weights of the rolls to be produced.
The rolls must be of high quality, which means, inter alia, that the material being wound must not have any points where there is overstretching or initial tearing, that no folds are formed in the material and that winding is performed firmly enough that the individual turns do not slip over the winding core and shift telescopically in the direction of the winding core axis. Also required is a continuously high working rate, and in order to meet this requirement a changing of the finished roll for an empty winding core while the winder is running is envisaged. Such a change must be carried out to a possible extent without any material loss. Furthermore, the contact pressure or the clearance between the roll and winding drum is to be both constant during a winding operation and able to be set in adaptation to the material to be wound.
EP-A-O 394 197 discloses a winder on which rolls are produced by contact-winding, that is with the winding drum in contact with the roll produced. In the case of this winder, both the winding cores and the winding drum are driven during the winding operation. The winding cores are received in a winding core carrier which is fixed in place during the winding operation, which is referred to as "static" mounting. The winding drum is mounted displaceably, perpendicularly to its axis of rotation, which is referred to as "dynamic" mounting. In a comparison with an arrangement in which the rolls, or the winding cores, are mounted "dynamically" and the winding drum is mounted "statically", this has the advantage that the contact pressure can be kept at a constant value without any problems. This keeping-constant of the contact pressure is made more difficult in the case of a "dynamic" mounting of the rolls due to the fact that their dimensions and weights change during the course of the winding operation and can assume high values. In the case of the winder mentioned, the winding drum is displaced during the production of a roll from a forward position in the vicinity of the winding core at the beginning of the winding operation to a rearward position caused by the growing roll, to be precise against the force of an adjusting device, which serves the purpose of keeping the contact pressure constant between the winding drum and roll, which is necessary for the production of a roll of good quality.
The disadvantage of this winder is that the winding drum is displaced over a distance which is approximately the same size as the radial difference between the winding core and the finished roll. This has the consequence that the material loss which occurs during the changing of a wound winding core for an empty winding core is relatively great. In addition, with this winder, winding can only be performed by the contact process, so that it cannot be used for processing materials which have to be wound by the gap-winding or clearance-winding process, i.e., in which the winding drum and the roll must not touch during the winding operation.